1. Field
The presently disclosed subject matter relates to a vehicle headlight.
2. Description of Related Art
So-called projector vehicle headlights, such as automotive headlights, have been known. The projector headlights reflect light emitted from a bulb with a reflector to illuminate an area in front of a vehicle through a projector lens.
In the projector headlights, a bulb is typically inserted into a reflector through the back part of the reflector and is fixed, with the bulb extending along the optical axis of a projector lens in the front-back direction. In recent years, however, in order to reduce the front-to-back length of headlights, different type of headlights have been proposed where a bulb is inserted into a reflector through the side part of the reflector in the direction perpendicular to the optical axis and is fixed thereat (See Japanese Utility Model Application Laid-Open No. 2-47704, for example).
By the way, the amount of light emitted from the bulb is the largest in the direction perpendicular to the bulb-axis direction in which the bulb extends, and the smallest in the bulb-axis direction. As a result, headlights with a bulb inserted through the side part of a reflector cannot deliver sufficient amount of light in the front direction because only a small amount of light is incident on the side part of the reflector surface that lies ahead of the end of the bulb in the bulb-axis direction. In particular, when providing a low-beam light distribution, it becomes more difficult to provide sufficient amount of light because a shade blocks a part of light from the reflector.
In view of the above characteristics and problems, a vehicle headlight disclosed in Japanese Patent Application Laid-Open No. 2005-100766, as illustrated in FIG. 7, has been proposed. In this vehicle headlight, a bulb 82 is inserted into a reflector 83 through the side part (left part) of the reflector 83 so that the bulb 82 is perpendicular to the optical axis Ax of a projector lens 81. In addition, a first additional reflector 85 and a second additional reflector 86 are added. The first additional reflector 85 is provided between the bulb 82 and a shade 84; and the second additional reflector 86 is provided in the side part of a reflection surface 83a of the reflector 83, which side part lies ahead of the end of the bulb 82 in the bulb-axis direction (that is, the side part is to the right of the end of the bulb 82). As indicated by arrows in FIG. 7, the first additional reflector 85 reflects direct light from the bulb 82 to the back direction, and the second additional reflector 86 in turn reflects the light from the first additional reflector 85 to the vehicle-front direction.
In this way, the vehicle headlight disclosed in Japanese Patent Application Laid-Open No. 2005-100766 utilizes the side part of the reflection surface 83a, on which only a small portion of light directly emitted from the bulb 82 is incident, by placing the second additional reflector 86 thereon. Further, the vehicle headlight makes efficient use of light, which would have been blocked by the shade 84, with the first additional reflector 85 and the second additional reflector 86. Thus, the vehicle headlight can increase available luminous flux and can deliver sufficient amount of light in the front direction.
However, in the vehicle headlight disclosed in Japanese Patent Application Laid-Open No. 2005-100766, the first additional reflector 85 is simply disposed between the bulb 82 and the shade 84, which makes a space around the bulb 82 narrow. As a result, heat from the bulb 82 is not easily escaped, which causes a problem of the rise in temperature around the bulb 82.